The present invention relates to an actuator for sub-sea valves.
Valve assemblies in sea-bed pipeline installations comprise a valve housing proper, generally with a ball element, and a separate actuator, that is, a directly or remotely controlled device by which the valve is opened and closed.
Conventional actuator systems are mostly hydraulic, comprising a hydraulic pump and a control circuit by which oil is forced into a chamber accommodating a piston; the piston operates a rack-and-gear drive of which the gear is keyed to a shaft, this shaft being coupled in turn to the shaft of the valve. Such actuators require periodic maintenance, which must be effected out of water, and therefore have to be removed from the pipeline at given intervals. Accordingly, the coupling between the shafts of the actuator and the valve must be such as to enable swift removal of the actuator, not least in the event of malfunction or breakdown occurring.
The conventional systems used currently to couple actuators and valves are notably time-consuming, in particular when connecting the components together; these are underwater operations repeated many times over and at considerable depth, where, as is well known, the ability of a person to operate at full physical and mental capacity is notably impaired. More exactly, the conventional systems in question involve coupling the shaft of the actuator to the keyed shaft of the valve; to facilitate alignment of the two parts, use is made of frames, bolted to the valves, by which the actuator is guided onto the valve shaft until fully home.
With the coupling effected, a plurality of bolts must be tightened to clamp together two flanges associated respectively with the actuator and the valve. This tightening operation requires a certain expenditure of physical energy on the part of the diver, besides taking time to complete; both are factors contributing ultimately to produce a high maintenance cost per actuator.
The object of the present invention is to bring about a notable reduction in the amount of time required to fit and remove sub-sea actuators, and to facilitate the task of the diver considerably by eliminating the need for energy-sapping maneuvers and decisions or calculations, the difficulty of which increases at depth.
A further object of the invention is to enable a simple diagnosis of the working efficiency of the actuator or the valve without the need to detach the one from the other.